making a long term career out of this kind of work is actually unappealing to some pooners...there are some people out there that prefer that part-time student or single mom etc type that is an amateur and is just doing this for a short time to save up blah blah, and get turned off if an SP has been doing this for a few years...Its the same sort of mentality that comes with judging promiscuous women, yet praising men who do the same (rude and disrespectful IMO), because the customer gets to poon a lot longer than the SP they are insulting.
In any case, if this is going to be a long term venture, its best to play it safe most of the time or at least by default, and take lots of breaks or cut down at times periodically